The invention relates to a pneumatic ride level control system for a motor vehicle composed of a pneumatic spring, a connecting line which connects the pneumatic spring to an atmospheric port, and a first valve which, in a first switched state, disconnects the connecting line and, in a second switched state, clears it.
In modern motor vehicles, pneumatic springs are being used to an increasing degree in suspension systems since they permit comfortable suspension and adjustment of the ride level of the motor vehicle frame with respect to the underlying surface. For reasons of vehicle movement dynamics and driving safety it is highly significant that the ride level which is set after loading or unloading of the vehicle has taken place no longer changes, in particular while traveling.
Document DE19710399C2 discloses an arrangement having an air spring and an additional volume, in which the additional volume is connected to the air spring by means of a connecting line which has a large cross section. The connecting line can be cleared or disconnected by means of a valve, depending on the level of comfort required of the suspension. Such air suspension systems are usually equipped with an electronic or pneumatic ride level control system which is complicated in design and costly and therefore expensive.
Application document DE102004043492.1, which was not published before the priority date of the present document, discloses a device for identifying the reference driving position of a motor cycle which is provided with pneumatic suspension. The device has a spirit level in the field of vision of the driver so that the driver or some other person can change the pressure in the pneumatic spring when the motor cycle is stationary, before travel is started, and can therefore set the ride level of the motor cycle. This can either by done by filling the pneumatic spring by means of a hand pump or a pressurized gas bottle in order to raise the ride level or by opening a valve and letting out some of the compressed air from the pneumatic spring into the atmosphere. A disadvantage with this arrangement is that the driver cannot change the ride level while traveling, the ride level having been adjusted, for example, as a result of a change in temperature of the pressurized gas inside the pneumatic spring. In particular the described discharge function can be carried out by the driver only in the stationary state of the motor cycle, and even then only with a restricted degree of accuracy owing to the discharge valve which is activated by the driver and the opening time behavior of said valve.
The invention is therefore based on the object of providing a pneumatic ride level control system of the type mentioned at the beginning in which an at least incremental change in the ride level can be carried out easily by the driver of the motor vehicle while the vehicle is traveling.